Tunnel support including a yieldable connection



Dec. 3, 1968 J. H. ROCK L 3,413,313

TUNNEL SUPPORT INCLUDING A YIELDABLE CONNECTION Filed March 9, 1966 2 Sheets-Sheet 1 J) .J. 5 Y? Z INVENTORS JAMES H. ROCK, 110 m 5 Alva 5950A] .92; 44/4 70/1/ I 506K/4/AZ75? ig/Md ATTO RNEYS J. H. ROCK ET AL 3,413,813

TUNNEL SUPPORT INCLUDING A YIELDABLE CONNECTION Dec; 3, 1968 2 Sheets-Sheet 2 Filed March 9. 1966 III III! ,5 mMm Wm? Ham s w w M M w W ATTORNEYS nited States Patent 0 3,413,813 TUNNEL SUPPORT INCLUDING A YIELDABLE CONNECTION James H. Rock, Sewickley, 1 21., Lloyd E. Anderson, Sr., Des Moines, Iowa, and Milton Thomas Buckwalter, Allison Park, Pa, assignors to Pittsburgh-Des Moines Steel Company, Pittsburgh, Pa., a corporation of Pennsylvania Filed Mar. 9, 1966, Ser. No. 532,943 9 Claims. (Cl. 61-45) ABSTRACT OF THE DISCLOSURE A pair of rigid tunnel supporting ribs each have a web and the adjacent ends of the ribs are spaced apart. Means for connecting the ends of the ribs comprises a pair of rigid channel members each having webs engaging webs on the ribs for clamping the end portions of the ribs between the channel members. Rigid filler means is disposed between the channel members and in contact therewith, the filler means being spaced from at least one of the end portions of the ribs to permit relative movement between the parts and absorbing excess loading by controlled friction.

The present invention relates to a new and novel tunnel support including a yieldable connection, and more particularly to an arrangement which reduces the probability of local failure in tunnel supports.

The tunnel support of the present invention is of a type wherein a plurality of supporting ribs are provided for supporting various types of overburden. The overburden often includes one or more faults which may cause the forces applied to the supporting ribs to vary as the overburden shifts from time to time. These changes in the forces applied to the supporting ribs have often resulted in local failure in tunnel supports of conventional construction.

The supporting ribs as employed in tunnel supports are designed primarily for uniform compression load and secondarily for local bending. This is because of the local conditions causing bending may or may not exist and are impossible to correctly evaluate. Therefore, it is most desirable to have the greatest margin between design and ultimate capacity in the supports.

The arrangement of the present invention provides an additional margin of safety by providing connections or joints between the spaced adjacent end portions of the supporting ribs, these connections being so constructed as to yield as the load exceeds the design load and to transfer part of the overload to the adjacent supporting ribs. During the period of yielding and transferring of loads, the supporting ribs are not being overstressed, the excess load being absorbed by controlled friction. It is also desirable to ensure that the dimensions of the tunnel are maintained, and accordingly, the present invention incorporates means for limiting the distance that the friction brake functions. When this limit is reached, the supporting ribs positively stop from further movement, and the supporting ring or natural pressure arch formed by the various interconnected supporting ribs will function to its ultimate capacity.

In other words, the yieldable connection means between the supporting ribs prevents failure of the ribs due to excessive unbalanced loading from the overlying strata of soil and rock. As excessive pressure is applied to a supporting rib, the yieldable connection will yield slowly allowing the unbalanced forces to be transferred to the surrounding ground with the formation of a resulting natural pressure arch.

3,413,813 Patented Dec. 3, 1968 The yieldable connection of the present invention is so designed that it can accommodate a variable distance between the adjacent end portions of the two associated supporting ribs which it joins. This compensates for variations in the supporting rib circumferences which are encountered in various tunnels.

The number of yieldable connections provided will vary according to the size of the tunnel. A single or multiple number of connections will function, and for larger diameter tunnels, more yieldable connections are desirable.

The capacity of a given size of compression member varies with its length, and the yieldable connection must yield at the design capacity. This can be controlled in the present invention by the size of the bolts employed in the nut and bolt assemblies, the number of bolt and the tension in the bolts. Accordingly, means is provided for controlling the yielding point of the connection.

The yieldable connection of the present invention also serves as a guide during the period of yielding to keep the adjacent end portions of the supporting ribs aligned with one another, and the stiffness of the yieldable connection equals the stitfness of the rib so as to provide adequate ultimate capacity of the over-all construction.

An object of the present invention is to provide a new and novel tunnel support including a yieldable connection which reduces the probability of local failure in the tunnel support due to excessive unbalanced loading by the overburden.

Another object of the invention is the provision of a tunnel support including a yieldable connection wherein the yieldable connection will yield as the load exceeds the design load and transfers part of the overload to the adjacent supporting rib-s.

Still another object of the invention is to provide a tunnel support including a yieldable connection which prevents overstressing of the supporting ribs during the period of yielding and transferring, the excess load being absorbed by controlled friction.

A further object of the invention is the provision of a tunnel support including a yieldable connection including means for positively limiting the distance that the friction brake functions so that the dimensions of the tunnel are maintained within adequate tolerances.

A still further object of the invention is the provision of a tunnel support including a yieldable connection which acts as a guide during the yielding period to keep the ends of the supporting ribs aligned with one another and wherein the stiffness of the yieldable connection is equal to the stiffness of the supporting ribs.

A still further object of the invention is to provide a tunnel support including a yieldable connection which accommodates variable distances between the ends of the supporting ribs to compensate for different rib circumferences in different tunnels.

Yet another object of the invention is the provision of a tunnel support including a yielding connection which is quite simple and inexpensive in construction and yet which at the same time is quite efiicient and reliable in operation.

Other objects and many attendant advantages of the invention will become more apparent when considered in connection with the specification and accompanying drawings, wherein:

FIG. 1 is a cross section through a tunnel illustrating a tunnel support according to the present invention;

FIG. 2 is a front elevation of a first form of the invention as employed in FIG. 1;

FIG. 3 is a sectional view taken substantially along line 33 of FIG. 2 looking in the direction of the arrows;

FIG. 4 is a front elevation of a modified form of the invention;

FIG. 5 is a sectional view taken substantially along line 55 of FIG. 5 looking in the direction of the arrows;

FIG. 6 is a front elevation of a still further modified form of the invention;

FIG. 7 is a sectional view taken substantially along line 77 of FIG. 6 looking in the direction of the arrows;

FIG. 8 is a front elevation of still another form of the invention;

FIG. 9 is a sectional view taken substantially along line 99 of FIG. 8 looking in the direction of the arrows;

FIG. 10 is a front elevation of still another form of the invention; and

FIG. 11 is a top view of the structure shown in FIG. 10.

Referring now to the drawings wherein like reference characters designate corresponding parts throughout the several views, FIG. 1 illustrates a typical tunnel support arrangement wherein the overburden is indicated by the letter O, and a pair of spaced fault lines and 22 are indicated in the overburden. It will be readily recognized that in an overburden having fault lines of this nature, the

soil and rock of a typical overburden may shift so as to produce unbalanced loading on the supporting ribs.

In the illustrated construction, four spaced supporting ribs or rib segments are indicated by reference numerals 30, 32, 34 and 36. It will be readily apparent that the number of supporting ribs may vary according to the size of the tunnel. Three spaced yieldable connections are indicated generally by reference numerals 38, 40 and 42, it being apparent that each of these yieldable connections serves to interconnect the adjacent spaced end portions of a pair of the Supporting ribs. The opposite supporting ribs 30 and 36 are in turn supported on suitable base means 44 and 46 of a conventional nature.

It should be understood that various forms of the yieldable connection are illustrated in the different figures of the drawing, and that any of the various forms of the invention may be incorporated for the yieldable connections shown in FIG. 1.

Referring now to FIGS. 2 and 3, the details of construction of a first form of the invention are illustrated, and a pair of supporting ribs are indicated generally by 50 and 52, these supporting ribs each having a structural shape and in the illustrated embodiment being of I-shaped cross sectional configuration and including central inter mediate web portions 50 and 52 respectively. The end portions 54 and 56 of the supporting ribs 50 and 52 respectively are spaced a substantial distance from one another, and this spacing may be varied as desired.

A pair of connection members 60 and 62 are provided, each of these connection members being channel-shaped or U-shaped in cross sectional configuration and including central web portions 60 and 62 which are disposed in spaced parallel relationship to one another. The connection members engage opposite sides of the web portions of the supporting ribs and the connection members further extend longitudinally along the associated supporting ribs for a substantial distance as will be noted in FIG. 2. The connection members accordingly are adapted to clamp the webs of the supporting ribs therebetween.

It is apparent that the connection members are of substantially similar construction and are of less height than the supporting ribs so as to permit the connection members to be placed in the operative position illustrated.

Securing means is provided for interconnecting the connection members, and in this form of the invention, a pair of holes is provided in each of the connection members, these holes being aligned with one another so as to receive a pair of bolts 66 having nuts 68 threaded thereon for clamping the strutcure in the operative position shown. It will be noted that these nut and bolt assemblies are associated only with the connection members and are spaced from the adjacent end portions of the supporting ribs, and accordingly, it is not necessary to provide any cuts or holes in the supporting ribs themselves.

The structure illustrated in FIGS. 2 and 3 is designed to yield at a low nominal load and after slipping through a predetermined distance is to develop an ultimate strength equal to the working stress of the rib which may be approximately 15,000 p.s.i. times the cross sectional area of the rib. This connection depends on the wedge action between the connection members to resist the tendency to slip. After yielding starts, the resistance to further yielding increases up to the point that the web of each of the supporting ribs engages or bears against the bolts 66. After this point is reached, the ultimate strength of the construction depends on the shear strength of the bolts and the bearing strength of the web of the supporting ribs.

It should be noted that the load at which yielding starts may be controlled in this modification as well as the modification described hereinafter by adjusting the torque on the bolts. The greater the torque, the greater the load at which the connection starts to yield, but in each case the ultimate load capacity of the arrangement will remain the same.

Referirng now to FIGS. 4 and 5, a modification is illustrated wherein a pair of supporting ribs 70 and 72 are provided, these supporting ribs also being of generally I- shaped cross sectional configuration and including central intermediate web portions 70' and 72'. The end portions 74 and 76 of the supporting ribs are spaced from one another, and the spacing between such end portions may be varied as required.

The connection means includes a pair of connection members 80 and 82 each of which is of channel or U- shaped cross sectional configuration, these connection members including intermediate spaced substantially parallel web portions 8% and 82 respectively.

In this form of the invention, a filler means is provided between the connection members and comprises a fiat place 84 which snugly fits between the connection members and is thinner than web portions 70' and 72. This filler plate has a height approximately the same as that of the supporting ribs 70 and 72.

The connection members 80 and 82 and the filler plate 84 are provided with aligned holes formed therethrough for receiving a pair of bolts 86 having nuts 88 threaded thereon whereby the various components may be clamped in the operative position shown such that the connection members 80 and 82 serve to clampingly engage the web portions of the two adjacent supporting ribs as well as to clamp the filler plate therebetween.

This form of the invention is also designed to yield at a low nominal load and after slipping through a predetermined distance is adapted to develop an ultimate strength equal to the working stress of the rib which may be approximately 15,000 p.s.i. times the cross sectional area of the rib. This yieldable connection depends on the friction between the connection plates and the webs of the supporting ribs to resist yielding. After yielding occurs, the ultimate strength of the connection depends on the bearing between the opposite ends of the filler plate and the webs of the adjacent supporting ribs.

Here again, as in each of the modifications of the present invention, the load at which the yieldable connection starts to yield may be controlled by adjusting the torque on the bolts.

Referring now to FIGS. 6 and 7, a still further modification of the invention is illustrated wherein a pair of supporting ribs 90 and 92 are provided, these supporting ribs also being of generally I-shaped cross sectional configuration and including intermediate central web portions 90' and 92 respectively. The ends 94 and 96 of these ribs 90 and 92 respectively are spaced a substantial distance from one another, and this spacing may be varied as desired.

A pair of connection members 100 and 102 are provided, each of these connection members being of channel or U-shaped cross sectional configuration and have central web portions 100 and 102' respectively which are disposed in spaced parallel relationship to one another and are adapted to clampingly engage the web portions of the associated supported ribs as in the previously described modifications.

In this form of the invention, the filler means includes a pair of separate spaced filler members 110 and 112, filler member 110 being in engagement with the end portion 96 of supporting rib 92, and filler member 112 being in engagement with the end portion 94 of the supporting rib 90. It will be noted that the adjacent end portions of the filler members 110 and 112 are spaced from one another.

First securing means includes a pair of bolts 114 having nuts 116 threaded thereon, these bolts extending through holes provided in the central web portion of filler member 110 which is of generally I-shaped cross sectional configuration as seen in FIG. 7 and which may be substantially identical to the cross sectional configuration of supporting rib 92, the bolt 114 also extending through slots 120 formed in each of the connection members and 102. As seen particularly in FIG. 6, slots 120 extend longitudinally of the associated connection members and permit sufiicient movement of the various components with respect to one another so that the adjacent end portions of the filler members and 112 may eventually come into contact with one another. It will be noted that substantially square shaped washers 122 and 124 are disposed in engagement with the Web portions 102' and 100' respectively in overlying relationship to the slots formed in the connection members.

Second securing means is provided for securing the connection members and filler member 112 together, it being understood that filler member 112 may also be of substantially I-shaped cross sectional configuration corresponding to the cross sectional configuration of supporting rib 90. A pair of bolts extend through suitable aligned holes provided in the connection members 100 and 102 and the filler member 112 whereby these components are interconnected with one another, it again being noted that no holes need be formed through the web portions of the supporting ribs themselves, and that the torque on the bolts may be adjusted to control the load at which the connection starts to yield.

This form of the invention is designed to yield at a load equal to the working stress of the rib times the cross sectional area of the rib and after slipping through a pre determined length, the connection will develop the full ultimate strength of the supporting rib. Here again, the yieldable connection initially develops frictional resistance to slipping and the connection develops the ultimate strength of the supporting rib by the bearing between the ribs and the filler means.

Referring now to FIGS. 8 and 9, a still further modification of the invention is illustrated wherein a pair of adjacent tunnel supporting ribs are indicated by reference numerals and 142 and are generally I-shaped cross sectional configuration and include central intermediate Web portions 140' and 142 respectively. The adjacent end portions 144 and 146 of the ribs 140 and 142 are spaced from one another, and this spacing may be varied as desired.

A pair of connection members 150 and 152 are provided, these connection members being generally channel or U-shaped in cross sectional configuration and including central web portions 150 and 152' respectively which are disposed in spaced parallel relationship to one another and which are adapted to clampingly engage the web portions of the associated ribs.

In this form of the invention, a pair of filler plates and 162 are provided, plate 160 being in engagement with the end portion 144 of rib 140, and plate 162 being in engagement with the end portion 146 of rib 142. It will be noted that the filler plates 160 and 162 are spaced from one another.

First securing means includes a pair of bolts 164 having nuts 166 threaded thereon, these bolts extending through suitable holes provided in plate 160 and longitudinally elongated slots 168 provided in the connection members 150 and 152 respectively.

In a similar manner, bolts 170 are provided having nuts 172 threaded thereon, bolts 170 extending through suitable holes provided in plate 162 and aligned elongated slots 174 provided in the connection members 150 and 152. This arrangement permits the Web portions of the associated supporting ribs to be clamped between the connection members and the filler plates also snugly clamped in operative position as illustrated. The length of the slots 168 and 174 is such as to permit the two filler plates 160 and 162 to eventually bear against one another to develop the ultimate strength of the connection. Here again, the load at which the connection starts to yield may be controlled by adjusting the torque on the bolts.

Referring now to FIGS. 10 and 11 of the drawings, still another modification of the invention is illustrated wherein a pair of supporting ribs and 182 are provided and which may also be of generally I-shaped cross sectional configuration including central intermediate web portions 180 and 182 respectively. The adjacent end portions 184 and 186 of ribs 180 and 182 respectively are spaced from one another, and this spacing may be varied as desired.

A pair of connection members 190 and 192 are provided which may be similar to those previously described, the connection members being generally channel or U- shaped in cross sectional configuration and having central spaced parallel web portions adapted to clampingly engage opposite sides of the webs of the associated supporting ribs. One end portion of connection member 190 is rigidly fixed to one side of supporting rib 180 as by welding indicated by reference character .194. The other connection member 192 is rigidly fixed to the opposite side of the other supporting rib 182 as by similarly welding the upper and lower portions of the connection member to the associated supporting rib as indicated at 196 in FIG. 11. Accordingly, the connection members are rigidly fixed to opposite sides of the two different supporting ribs, one end of each of the connection members being in sliding contact with the supporting rib other than that to which it is fixedly secured.

The filler means in this form of the invention comprises a single flat plate 200 which is in engagement with the end portion 186 of rib 182 and which is spaced from the end portion 184 of the other rib 180.

The securing means in this form of the invention comprises a pair of spaced bolts 204 having nuts 206 threaded thereon. The bolts extend through suitable holes provided in the filler plate 200 and longitudinally extending elongated slots 208 provided in the connection members 190 and 192. I

It is apparent from the foregoing that there is provided according to the present invention a tunnel support including a yieldable connection which reduces the probability of local failure in tunnel supports due to excessive unbalanced loading from the overburden of soil and rock or the like. The yieldable connection is adapted to yield in each case as the load exceeds the design load, the point of yielding being controllable by adjusting the torque on the bolts, and the yieldable connection transfers part of the overload to adjacent supporting ribs. The yieldable connections of the present invention prevent overstressing of the supporting ribs during the period of yielding and transferring of loads, the excess load being absorbed by controlled friction. Means is provided for positively limiting the distance that the friction brake functions so that the dimensions of the tunnel are maintained within necessary tolerances. The connection in each case acts as a guide during the yielding period and keeps the ends of the associated supporting ribs aligned with one another. The yieldable connection also has a stiffness which is equal to that of the rib so as to enable the construction to develop the desired ultimate strength. The yieldable connection of the present invention also will accommodate variable distances between the ends of adjacent supporting ribs to compensate for different rib circumferences in different size tunnels. The arrangement of the present invention is quite simple and inexpensive in construction, and yet at the same time is quite efficient and reliable in operation.

As this invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, the present embodiment is therefore illustrative and not restrictive, and since the scope of the invention is defined by the appended claims, all changes that fall within the metes and bounds of the claims or that form their functional as well as conjointly cooperative equivalents are therefore intended to be embraced by those claims.

We claim:

1. A tunnel support including a pair of rigid tunnel supporting ribs each having a web, the adjacent end portions of said ribs being spaced from one another, connection means for connecting said spaced adjacent end portions, said connection means including a pair of rigid channel members each having a web, the webs of said pair of members engaging opposite sides of the web of each of the end portions of the associated supporting ribs for clamping said end portions between said pair of members, rigid filler means disposed between said pair of members and in Contact with said pair of members, said filler means being of a height substantially at least as great as that of the webs of said rigid channel members, said filler means being spaced from at least one of said end portions of the associated supporting ribs, and clamping means for interconnecting said pair of members and said filler means with one another.

2. Apparatus as defined in claim 1 wherein each of the members of said pair of members and said filler means have aligned holes formed therein, said clamping means including at least one nut and bolt assembly extending through said aligned holes.

3. Apparatus as defined in claim 1 wherein said channel members are spaced from one another and extend longitudinally a substantial distance along opposite sides of said rib web portions, said filler means including a substantially flat intermediate portion fitting snugly between said pair of members, said pair of members and said filler means having holes formed therethrough and aligned with one another, said clamping means comprising at least one nut and bolt assembly extending through said aligned holes for clamping said pair of members and said filler means to one another and developing a predetermined frictional resistance to movement, said nut and bolt assemblies being spaced from the end portions of the associated supporting ribs.

4. Apparatus as defined in claim 3 wherein the holes formed in said pair of members comprise elongated slots extending longitudinally of said pair of members.

5. Apparatus as defined in claim 1 wherein said filler means comprises a fiat plate.

6. Apparatus as defined in claim 1 wherein said filler means comprises a pair of separate members spaced from one another.

7. Apparatus as defined in claim 6 wherein said supporting ribs have an I-shaped cross sectional configuration, and wherein said pair of filler members are also of I-shaped cross sectional configuration.

3. A tunnel support including a pair of tunnel supporting ribs the adjacent end portions of which are spaced from one another, connection means for connecting said spaced adjacent end portions, said connection means including a pair of members, said pair of members engaging opposite sides of each of the end portions of the associated supportin ribs for clamping said end portions between said pair of members, filler means disposed be tween said pair of members and in contact with said pair of members, said filler means being spaced from at least one of said end portions of the associated supporting ribs. and clamping means for interconnecting said pair of members and said filler means with one another, said filler means comprising a pair of spaced members, said securing means including a nut and bolt assembly associated with each of said filler members, each of said nut and bolt assemblies extending through holes provided in said pair of connection members and the filler members therebetween, each of the holes formed in the connection members comprising an elongated slot extending longitudinally of the connection member, said filler members being normally spaced from one aonother, and said slots being of such a length as to permit the filler members to engage one another to limit the relative movement be tween the various components of the apparatus.

9. A tunnel support including a pair of tunnel supporting ribs the adjacent end portions of which are spaced from one another, connection means for connecting said spaced adjacent end portions, said connection means including a pair of members, said pair of members engaging opposite sides of each of the end portions of the associated supporting ribs for clamping said end portions between said pair of members, filler means disposed between said pair of members and in contact with said pair of members, said filler means being spaced from at least one of said end portions of the associated supporting ribs, and clamping means for interconnecting said pair of members and said filler means with one another, one of said connection members being fixedly secured to one side of one of said supporting ribs, the other of said connection members being rigidly fixed to the opposite side of the other of said supporting ribs, said connection members and said filler means having aligned holes formed therethrough, and said securing means comprising at least one nut and bolt assembly extending through said aligned holes and spaced from the end portions of said supporting ribs.

References Cited FOREIGN PATENTS 513,282 11/1930 Germany. 525,396 5/1931 Germany. 633,681 8/1936 Germany. 909,178 10/1962 Great Britain. 1,174,279 7/ 1964 Germany.

JACOB SHAPIRO, Primary Examiner. 

